I. Field of the Invention
The present invention relates to washing machines and more particularly to a motor cut-off for washing machines.
II. Description of Prior Art
Washing machines are commonplace in most homes. A typical washing machine includes a drive system having a motor operatively coupled to a drive shaft. The drive shaft includes a first or input shaft which rotates in response to the motor such as via a pulley and brake mechanism. The input shaft is coupled to a transmission having a second or output shaft of the drive shaft, and which in turn supports a clothes basket within a water tub, and an agitator for selective rotation with the clothes basket. In one mode of operation, such as during wash and rinse cycles, the output shaft is caused to rotate back and forth so as to rotate the basket and/or agitator back and forth to thus agitate the clothes and water in the basket for cleaning or rinsing of the clothing. In another mode, such as during the spin cycle, the output shaft spins quickly so as to spin the clothes basket and remove water from the clothing by centrifugal force.
The controls of the washing machine typically include a timer or other components or circuitry which output signals to selectively energize and deenergize the motor, and control other functions of the washing machine, as necessary for washing clothes. The signal to the motor may be coupled from the controls to a motor drive circuit. The motor drive circuit, in turn, is coupled between the power and ground rails of the machine so as to power the motor. When the basket is spinning, such as during the spin cycle of the machine, it is desired to prevent users from sticking a hand into the area of the basket. To that end, the washing machine normally includes a lid that must be in the closed position for the basket to spin. A lid switch may be mounted to the machine near the lid to detect if the lid is opened during the spin cycle (as well as possibly during other cycles, if desired). The lid switch may include a magnet mounted to the lid, and a reed switch mounted to the machine housing adjacent the lid. The reed switch would typically be in series with the motor drive circuit, or a portion thereof, such that when the reed switch indicates that the lid is open (e.g., the magnet is spaced away from the reed switch), no power can flow to the motor, and the clothes basket will slow down and stop spinning. Additionally, when the motor is deenergized, the brake associated with the drive shaft is supposed to react quickly to slow down and stop rotation of the shaft and thus the basket whenever opening of the lid is detected.
Should the brake fail, however, the basket will continue to spin until it slows down due to frictional and other forces inherent in the machine. Unfortunately, if the brake fails, further use of the machine may expose the user to harm because each time the basket spins, opening of the lid will no longer result in a prompt cessation of the spinning motion. To avoid that problem, the controls may be shut down or otherwise rendered inoperable so that they cannot provide a signal to the motor drive circuit until after a service technician has inspected and repaired the machine. As is known in the art, if, for example, the controls of the washing machine indicate that the spin cycle is over, but the speed of rotation continues to be too fast (such as indicated by a speed sensor associated with the drive shaft or clothes basket), a brake failure signal may be generated. The brake failure signal indicates that the brake has failed, or at least is no longer operating within acceptable parameters, and is used by the controls to shut down. Design of controls to cause them to shut down can be costly and complex, or may not be applicable to all washing machines.
The present invention provides a motor cut-off by which to permanently or temporarily prevent the motor from being energized after a brake failure, but which does not necessarily require that the controls be shut down or otherwise rendered inoperative. To this end, and in accordance with the principles of the present invention, included in series between the motor drive, or a portion thereof, and the power and ground rails is a fuse and a blow switch coupled to the fuse and one of the power or ground rails as appropriate by which to blow the fuse in response to the brake failure signal. Where a lid switch is used, the lid switch may also be in series therewith. When the fuse is blown, either permanently or temporarily (such as in the case of a resettable breaker), current cannot flow through the motor drive circuit, or portion thereof (irrespective of the state of the lid switch), thereby preventing the motor from being energizable until the fuse is either reset or replaced such as would be done in a service call.
By virtue of the foregoing, there is thus provided an improved brake failure safety system which eliminates the need for the controls in a washing machine to be shut down or rendered inoperative in the event of a brake failure. These and other objects and advantages of the present invention shall be made apparent from the accompanying drawings and the description thereof.